The claimed invention relates to a rotary pump. In particular, the invention relates to a fuel pump having an inlet ramp with desirable characteristics.
Regenerative fuel pumps are used in vehicles to pump fuel from a fuel tank through a fuel handling system to the engine of the vehicle. Fuel pumps typically include a driven ring impeller that rotates within a pump casing. The impeller has an upstream side and a downstream side. The pump casing includes a cover that is positioned adjacent the upstream side of the impeller and a body that is positioned adjacent the downstream side of the impeller. The pump casing also includes a cup, which serves as the outer shell that houses the cover, impeller, body and other pump parts.
The ring impeller has vanes, which are bounded by annular channels defined in the casing. The channels are positioned at the upstream and downstream sides of the impeller vanes within the casing. The channel at the upstream side of the impeller provides fuel to the impeller while the channel at the downstream side expels fuel from the impeller.
The channel at the upstream side of the impeller includes an inlet through which fuel enters the impeller. The upstream channel may include a ramp or several ramps depending on the design. It is desirable to limit the amount of vapor generated within the upstream channel. Vapor reduction helps to improve pump efficiency, which furthers high fuel flow rates under hot fuel conditions. The upstream channel may include a vapor vent hole, through which vapor may escape to minimize vapor within the fuel as it passes through the fuel pump.
A pump comprises a pump casing and an impeller. The pump casing has an axis and comprises a cover having a face surface and a body positioned about the axis. An arcuate channel is defined in the face surface of the cover and extends at least partially circumferentially about the axis. An inlet opening extends through the cover and is coupled to the arcuate channel. The impeller is positioned between the face surface of the cover and the body. The arcuate channel has a first section and a second section, with the first section extending from the inlet opening and being continually sloped relative to the face surface of the cover. The first section has a length of about 40 to about 90 degrees, as measured circumferentially on the face surface of the cover about the axis. The first section includes an inlet ramp, a main ramp, and a secondary ramp. The secondary ramp is positioned between the main ramp and the inlet ramp, and the inlet ramp is positioned adjacent the inlet opening. Each ramp has a depth and a slope. The depth of the inlet ramp is greater than the depth of the secondary ramp, and the depth of the secondary ramp is greater than the depth of the main ramp. The slope of each ramp is different from the slope of the other ramps.
The invention also concerns a cover incorporating the arcuate channel discussed above.